Plunger electromagnet



Dec. 30, 1947. E. F. MEKELBURG 2,433,703

PLUNGER ELECTROMAGNET Filed Feb. 5,v 1943 ing membersV L.

Patented Dec. 30, 1947 Earl F. Mekelburg, Wauwatosa,I Wis., assignor toSquare D Company, Detroit, .Mich., acorporation of MichiganApplcationFebruary 3, 1943*Serial No. 474,503`

4Claims.r 1

This invention relates tok an electromagnetic operatori'or an electric:Vswitch and has for its object the provision of such an operator: whichshall include a rectilinearly' movable plunger armature guided at itsopposite ends so. as to properly spacey the same from( the. stationarymagnetic elements.

Another object of the invention is the; provision of an electromagneticoperator for an electricl switch in which the operator inciudes aplunger armature having'i-ts rinterior end formed in the shape ofa'truncated cone Vseating within a complementary recess in a stationarymagnetic core member, the diameters ofv the cone and recess being suchas to preventA engagement of the sides of the cone and recesswhen thearmature plunger is seated.

Other objects and; features of the invention will be readily apparent tothose skilled in the art from the specication and appended drawingillustrating certain preferred errrbodimentsy in which:

Figure 1 is a side elevational View of the switch according tothepresentinvention with a portion y Figure 5 is a top plan view of theswitch with portions broken away.

The electric switch, as illustrated in the drawings, comprises a basecomposed of two plate members 2 and 3 formed of insulating material. A,pairl of' conducting connecting members, lY and 5, having contact faces5l and-1 provided aty the inner ends thereof are disposed at thelunderside of the base and haveprojections 6, and 9 thereon adapted to,be received within.openingsy and f2 provided in the insulating platemember 3 to thereby properly locate the connecting members 4, andl iiand to prevent. their turning. out of, position.; The connectingmembers4 and 5 are rigidly secured to the base i by a pair oi terminal studsi''and' ii, passing through aligned openings .in the cennectingmembers'and the' insulat 'i 3*, and their cooperating nuts l5 and' i'. Awasherr i? is disposed beneath each of the nuts 51 and E161 A secondpair of nuts land i9 are-providedon the'studs |f3 and lwhereby^ circuitwires (Snot. shown). maybe secureditothe switch'. A pair'oi. washers 2|land' 55H (Cl. 17E-341) 2 22v are providedbetween each. pair of nuts l5.and I8, and t6 and I9.

A magnetic plate 23A is carried on topy of. the base l and is securedthereto by rivets 24, one of which is illustrated rin Figure 1.` Therrivet 24 includes aguide portion 25 which is internally threaded andserves a purpose to beA hereinafter described. Ar second magnetic plate26 is dis posed within an opening 27| provided in insulating member 2and is sov positioned relative to plate 23 that an opening therein isplaced in alignment with anV opening provided through plate 23. Amagnetic sleeve or core member 28 having shoulder portions 2'9 issupported thereby on plate 23, and has a shank portion 3| which. extendsthrough the aligned openings of plates 23 and 26.. The rim of the shankportion 3|- is bent outwardly to hold plate 26 in intimate Contact withplateV 23-v and to rigidly secure. the sleeve member 28 in. position. Anenergizing coil 32 comprising a spool sleeve 33 of ber composition andspool washers 34, alsofof fiber composition, is disposed abou-tfthesleeve. 28 withV the latter member being contained except for the shankportion 3|, wholly within the opening in coil 32 provided by sleeve 33.A shell or cover 36 is tted over the coil 32'.. The. cover 36 isprovided with mounting flanges 31 which rest upon the magnetic plate 23.Studs... 33. passing through base and thefm-agnetic plate 23 arethreaded into the nanges 3'1 to thereby secure. shell 36 to the base. Afelt washer 39 is provided on top of the coil 32 and spaces the cover3,5 from the coil. A stationary core member 4|- having a recess 42extending'frorn the top surface thereof is carried by the covery 36,beingy secured thereto ink amar-incr similar: to that in which sleevemember 28 is secured to plate 23,. there beingshoulder portions: 43:provided on. the member 4| which bear against a magneticplate 44 and ashank portion. @which extends throughian opening in the cover,andthevrim. of. the shank portion is bent outwardly to rigidlyl X the,core member 4| in place. The core member4-| is provided with a recess loextending from its bottom surface and being of a truncated'cone shape.-VThe recess 42 extending fron-ith@V top surface of. member 4| and therecess extending from the bottom surface thereof' are. joined byVapassageway 41 for a-.purpose toibehereinafter described. Mount,- ing ofthe shell 36 in position. on the. base I. will place the greater portionof the core member 4I within theo-peiling in coil 32., but the length ofthe coremember 4| is. such` that the lower extremity thereofwillbe.spaced ay sufficient distance from core member 28 that fiux leakagetherebetween is held to a minimum.

Within recess 42 a spring seat 48 and a spring 49 are disposed. Asealing plate 5| is riveted to the cover 36 and closes the recess 42'and prevents access to within the cover 36. A boss 52 is formed in thesealing plate 5| and serves as a spring seat for positioning the upperend of spring 49. A second pair of terminal studs 54 and 55 are carriedby the base being held thereon by nuts 5S. To each of the studs 54 and55, a wire 57, leading from the solenoid coil 32, is secured by a stud58, las is also an external circuit wire (not shown) whereby electricalenrgy may be brought to the energizing coil 32. A plunger or armature 53is disposed within the sleeve member 28 and passes through an opening ininsulating member 2 and normally rests upon the surface of insulatingmember 3. A portion 59 of lesser diameter than the main body of thearmature 53 extends from the bottom portion thereof and through anopening 6| in the insulating member 3 and is closely received thereby. Aguide pin 62 formed of non-magnetic material is staked or otherwisesecured to the top surface of the armature 53 and extends throughpassageway 41 in core member 4| into recess 42. Spring seat 48 iits overthe end of pin 62 whereby upward movement of the armature 53 will beagainst the bias of spring 49. An extension 63 is provided at the end ofportion 59 of the armature 53 and supports a movable contact assembly orswitching member 64. The movable contact assembly 64 comprises a member65 formed of insulating material and a conducting member 68 rivetedthereto, with the conducting member 66 having an opening 6T through thecenter thereof and carrying contact surfaces 68 and 69 at opposite endsthereof adapted to bridge and cooperate with the stationary Contactfaces 6 and to make and break an electrical circuit therethrough. Raisedportions provided on the insulating member 65 space this member from theconnector 66. EX- tension 63 of the l'armature 53 passes through anopening in member 65 and through opening 61 in connector 66. To mountthe movable contact assembly 64 thereon, a springr member 13 with itsspring seats 14 is provided upon the extension 63 and held thereon by acotter pin '|5. The spring member 13 will normally exert its bias uponthe insulating member 65 to hold it in its, uppermost position andagainst shoulder portions 1S provided on portion 59 of armature 53 asshown in Figure 2. The insulating member 65 is slotted at either end Iasat and 18, and these slotted ends are disposed about guide portions 25and cooperate therewith to properly position the movable contactassembly 64 and to fix the path of movement thereof so that the Contactassembly will move in a substantially rectilinear path on movement ofthe armature or actuating member 53 unen energization and deenergizationof the coil 32. A cover 'I9 formed of molded Bakelite is disposed overthe movable contact assembly 64 to seal off the switch from outsideaccess. Studs 8| threaded into guide portions 25 secure the cover to thebase I.

A mounting bracket 82 is carried by the solenoid cover 3S whereby theswitch may be located in the desired location.

It is to be noted that the armature 53 is guided in its movements by theguide pin 62 and the armature portion 59. The pin 62 and the armatureportion 59 are closely received by the spaced concentric openings 41 and6| provided by core member 4| and the insulating member 3 and lateralmovement of the armature 53 and side pull thereon is thereby held to aminimum and there is no contact between the sides of the armature 53 andthe interior surface of sleeve member 28 on movement of the armature 53thereby avoiding friction loss.

With the construction here described, a more effective device issecured, for there is no necessity for the insertion of a brass sleeveor other liner between the interior surface of the sleeve member 28 andthe armature 53 and thus the air gap will comprise only the mechanicalclearance between the armature 53 and the sleeve member 28, and,therefore, the magnetomotive force required to move the armature ismaterially lessened over that which would be required if the air gapwere to include the thickness of a brass liner.

The lateral sides 83 defining the recess 46 in the stationary coremember 4| are of the same angle as the lateral sides 84 of armature 53but the diameter of the surface 85 defining the recess is slightlygreater than the diameter of the upper end 86 of the armature 53 so thatthere is no interference mechanically between the lateral surfaces 83 ofthe armature 53 and the lateral surfaces 84 defining the recess 46, andthe armature 53 will complete its full stroke into engagement withsurface 85 without frictional loss due to contact with the sides 83. Acomparatively steep cone angle is thus utilized to provide for arelatively high initial pull on the plunger 53 without the danger of theplunger sticking tight before a full stroke has been completed.

In the operation of the device of the present invention, assuming theparts to be in the position of Figure 2, energization of coil 32 willeffect an upward rectilinear movement of armature 53 against the bias ofspring 49 and into sealing engagement with surface 85. Movement of thearmature 53 carries extension 63 upwardly to apply force upon spring 13;this force is transmitted by the spring to the insulating member 65 tomove it also upwardly to thereby carry the movable contacts 68 and 69into bridging engagement with the stationary contacts 6 and 1 tocomplete a circuit therethrough. It is to be noted in Figure 4 that whenthe contacts are in engaged position there is a definite compression ofthe spring 49 which results in an application of force on the movablecontacts 68 and 69 to effect a substantial contact pressure betweenthese contacts and the stationary contacts 6 and 1.

On deenergization of the coil 32, the plunger 53 will move downwardlyunder the force of gravity and the bias of spring 49 to move the movablecontact assembly 64 and break the circuit. The device need not bemounted in vertical position as shown, for the spring 49 is madesuiciently stiff that it applies a force that will always return theplunger 53 to its deenergized position to break the circuit through theswitching assembly regardless of the position in which the device ismounted.

While certain preferred embodiments of the invention have beenspecifically disclosed, it is understood that the invention is notlimited thereto, as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims.

What is claimed is: n

1. An electromagnetic operator for an electric switch, comprising aninsulating base, a movable armature member, an energizing coil foreiecting movement thereof and having an opening therethrough, a pair ofcore members disposed within said opening in said energizing coil, saidcore members being spaced from one another and each of said core membershaving openings therein, said armature member being movable for thegreater part of its length within one of said core members, anon-magnetic member carried by said armature member and received by theopening in the second of said core members, and an extension on saidarmature member adapted to pass through an opening in said insulatingbase, said opening in said second core member and said opening in saidinsulating base being concentric whereby said armature member will beheld continually spaced from the sides of the core member through whichit moves for a greater part of its l-ength to effect an air gap betweenthe armature and the sides of said latter core member comprising onlythe mechanical clearance therebetween.

2. An electromagnetic operator for an electric switch, comprising anarmature member, an operating coil for effecting movement thereof andhaving an opening therethrough, a pair of magnetic members spaced fromone another and disposed at either end of said opening in said operatingcoil, the rst of said magnetic members having an opening therethroughand receiving said armature member for movement therein on energizationof said operating coil, means carried by said armature member forholding it spaced from the sides of said first magnetic member whenmoving therein to effect an air gap between said armature and rstmagnetic member, said armature member having an end portion thereofformed in the shape of a truncated cone, said second magnetic memberhaving a recess therein formed in the shape of a truncated cone and of asuiiiciently large diameter than the diameter of the end portion of thearmature that when said end portion of said armature member is received,upon energization of said coil, engagement with the sides of the recessis avoided.

3. An electromagnetic operator for an electric switch, comprising aninsulating base, a movable armature, an energizing coil for effectingmovement thereof from a, rst position, said ener gizing coil having anopening therethrough, a pair of magnetic members disposed within saidopening and spaced one from the other, the first of said magneticmembers having an opening therethrough and receiving said armature formovement therein on energization of said energizing coil, means forcentering said armature to prevent engagement with the sides of saidfirst magnetic member, and to eiect an air gap therebetween comprisedonly of the mechanical clearance between said armature and the sides ofsaid rst magnetic member, said means comprising a non-magnetic membersecured at one end of said armature member and being closely receivablewithin an opening in the second of said magnetic members and anextension on said armature member which is closely receivable within anopening in said insulating base, said second magnetic member having arecess therein into which said non-magnetic member extends and ismovable therein, spring means disposed in said recess and acting on saidnon-magnetic member to return said armature to said rst position upondeenergization of said coil.

4. An electromagnetic operator for an electric switch, comprising anarmature member, an operating coil for eiecting movement thereof, a pairof magnetic members spaced one from the other and disposed at either endof an opening in said operating coil, the first of said magnetic membershaving an opening therethrough and receiving said armature member formovement therein for the greater portion of its length on energizationof said operating coil, said armature member having an end portionthereof formed in the shape of a truncated cone, said second magneticmember having a recess therein formed in the shape of a truncated coneand of sufliciently larger diameter than the diameter of the end portionof the armature member that when said end portion of said armature isreceived, engagement with the sides of the recess is avoided, meanscarried by said armature member for holding it spaced from the sides ofsaid rst magnetic member when moving therein to form an air gap betweenthe armature and first magn-etic member, said means comprising anoninagnetic member provided at one end of said armature member and anextended portion at the opposite end of said armature member, saidnon-magnetic member extending into said recess in second magnetic memberand through a connecting passageway and into a second recess providedtherein, and spring means disposed in said second recess and acting onsaid non-magnetic member to return said armature to deenergize positionon deenergization of the coil.

EARL F. MEKELBURG.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,745,878 Trumpler Feb. 4, 19302,278,967 Allen Apr. 7, 1942 2,008,275 Dyer July 16, 1935 2,174,313 yCoffey Sept. 26, 1939 2,102,761 Strobel Dec. 21, 1937 2,297,626 LennholmSept. 29, 1942 '768,549 Stewart Aug. 23, 1904 978,377 Humphrey Dec. 13,1910 1,793,858 Lake Feb. 24, 1931 2,170,961 Borgkvist Aug. 29, 19392,238,154 Borgkvist Apr. 15, 1941 2,344,178 Sparrow Mar. 14, 19442,330,407 Claytor Sept. 28, 1943 FOREIGN PATENTS Number Country Date19,486 Great Britain 1906

